Three U.S. flights made unscheduled landings in the past eight days after passengers got into fights over the ability to recline their seats.

"Seats are getting closer together," said Sara Nelson, president of the Association of Flight Attendants, which represents 60,000 flight attendants at 19 airlines. "We have to de-escalate conflict all the time."

There are fights over overhead bin space, legroom and where to put winter coats.

"We haven't hit the end of it," Nelson said.

The International Air Transport Association calls unruly passengers "an escalating problem," saying there was one incident for every 1,300 flights in the past three years. The trade group would not share detailed historical data to back up the assertion that this is a growing problem.

To boost their profits, airlines have been adding more rows of seats to planes in the past few years. That means less room for passengers to spread out.

The latest spate of passenger problems started Aug. 24, when a man on a United flight prevented the woman in front of him from reclining. She dumped a cup of water on him.

Three days later, on an American flight from Miami to Paris, two passengers got into a fight, again over a reclining seat, and the plane was diverted to Boston.

Then on Monday night, on a Delta flight from New York to West Palm Beach, a woman resting her head on a tray table got upset when the passenger in front of her reclined his seat, hitting her in the head. That plane was diverted to Jacksonville.

There were 14,903 flight diversions by U.S. airlines in the 12-month period ending in June, according to an Associated Press analysis of Department of Transportation reports. That means, 41 flights a day, on average. Industry experts say the vast majority occur because of bad weather or mechanical problems.